The last straw for Sofia Vergara — who broke up with fiancé Nick Loeb last week — was Loeb’s hucksterism of his salad condiment product at the White House last year.

“She was appalled when he went to the White House as Sofia’s plus-one and sneaked in a container of Onion Crunch, which he tried to get the president to pose with,” said one source.

“He was on probation [for more than a year] with her after that, but, like a spoiled brat, never reformed.”

Last year, Loeb admitted to The Post that Vergara was not happy with his shameless promotion at the White House.

“When [Sofia] found out [Onion Crunch] was in my pocket, she made me put it back in the car,” he recalled. “But I snuck a couple of these little packets that I ended up handing to the executive chef at the White House.”

It wasn’t the only time he rode Vergara’s coattails.

“I brought [Onion Crunch] to the Emmys, the Golden Globes, the SAG awards,” he told The Post’s Hailey Eber. “I put them out on the tables or the buffets at the after-parties. I’ve taken pictures and tweeted them.”

Loeb is the son of John L. Loeb, a Reagan-era diplomat who was once the head of the Wall Street firm of Loeb, Rhoades & Company, and the great grand-nephew of former New York governor and banking heir Herbert H. Lehman.

The “Modern Family” bombshell liked Loeb’s tall, handsome looks, but not his sense of entitlement.

“Since Nick lives on the Loeb and Lehman trust funds and doesn’t want to have a real job, he is overbearing and bossy to be around,” said my source.

This isn’t the first time Loeb has been jilted. His stunning Swedish ex-wife Anna Pettersson fled less than two years after their lavish wedding in Stockholm, attended by various royals.

Maybe Sofia looked into her crystal ball and decided to save the cost of a bridal gown.